The present invention relates to a method and a radio station for transmitting information particularly by a mobile radio system, and further relates to the frequency channel arrangement used in such method and an appropriately adapted frequency channel search.
In conventional mobile radio systems such as the GSM (Global System for Mobile Communication) a multiple access method is used for utilizing the transmission capacities efficiently. In this method, the available frequency bands are also divided into a number of frequency channels in accordance with frequency division multiple access FDMA. For GSM operation, two frequency bands are reserved with 45 MHz band spacing: the 890 MHz to 915 MHz range for the uplink from the mobile station to the base station and the 935 MHz to 960 MHz range for the downlink operation from the base station to the mobile station. The frequency bands have a width of 25 MHz and are subdivided into 124 individual frequency channels of 200 KHz in each case. A frequency band is frequently divided further wherein the frequency subbands produced and the corresponding frequency channels are allocated to different network operators.
In future mobile radio systems, too, such as, the wide band CDMA system which is currently being standardized a frequency division multiple access method FDMA will be used together with a code division multiple access method CDMA. Such use possible will be in connection with another access method such as, for example, a time division multiple access method TDMA.
The present invention is thus directed toward arranging, structuring and allocating frequency ranges provided for communication via a mobile radio system to the individual network operators or subscribers, respectively, in such a manner that they can be used efficiently for transmitting information.
Accordingly, the present invention divides available frequency ranges into frequency bands (or at least one frequency band) and frequency channels, and arrange these frequency channels in accordance with a first coarse raster system and a second fine raster system, In such arrangement, at least the range of definition of the fine raster system is restricted.
Also in this arrangement, the coarse raster system can be described, for example, by a carrier spacing and the fine raster system can be described as subraster.
The result is that a certain frequency channel can be described using less information when this information is used for carrying out a correspondingly restricted frequency channel search, a network search or, respectively, synchronization can be carried out with less effort.
Another further development of the present invention provides that the coarse raster system and the fine raster system be respectively described by a variable information item and a constant information item. By storing the first constant information in a radio station and transmitting the second variable information between the radio stations, information for the unambiguous description of a frequency channel can be exchanged with less effort between the radio stations.
In a further embodiment of the present invention, the information is carried out in accordance with a CDMA method in which the radio signals spread by means of a CDMA code are transmitted essentially within a frequency channel. The arrangement of the frequency channels in accordance with the raster system is adapted to the conditions of transmission in such a manner that interference between the radio signals of the frequency channels is reduced to the greatest possible extent.
The present invention also includes methods for transmitting information between a first base station and a first mobile station, and between second base station and a second mobile station in which a number of frequency channels are available for transmitting the information. The transmission of information between the first base station and the first mobile stations takes place at least from time to time via radio signals essentially within a first frequency channel. The transmission of information between the second base station and the second mobile station takes place at least from time to time via radio signals essentially within a second frequency channel. In this arrangement, the first and second base station also can be allocated to different network operators or different layers of an hierarchical cell system.
Contemplated within the scope of the present invention is that transmission is understood to be the transmitting and/or receiving of messages.
Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Preferred Embodiments and the Drawings.
FIG. 1 shows a block diagram of a mobile radio system;
FIG. 2 shows a diagrammatic representation of multiple access methods;
FIG. 3 shows a diagrammatic representation of a raster system for frequency channel arrangement in accordance with the teachings of the present invention; and
FIG. 4 shows a block diagram of a radio station.